1. Field of the Invention
This invention relates to a raster scan type display apparatus provided with an image memory having a plurality of planes and suitable for carrying out a graphic display.
2. Description of the Prior Art
The Japanese Patent Laid-Open Gazette No. Sho 59-114581 has disclosed a display apparatus which is provided with first and second plane memories to display the contents thereof in a raster scan type display, the display apparatus being provided with a video selecting switch, a video selector for generating plane selecting signals corresponding to assignment by the video selecting switch, and an AND gate connected to the output of each plane memory and switched in response to plane selecting signals so that the contents of first and second plane memories are displayed simultaneously or separately.
Such conventional art selects the plane memory corresponding to operation of the video selecting switch, whereby the content of each plane memory merely is displayed independently on the entire screen, or the contents of both the plane memories are merely superposed on the entire screen.
In other words, when the plane is selected, the content of each plane cannot be displayed inclusively on one screen.